Were They Christian?

It's almost impossible to know what the Founding Fathers believed... Sure you can extrapolate from their writings but it's important to realize the whole mythology and concept of the Founders is over blown. Jefferson and Adams for example became bitter enemies, although the worked together during the revolution. It wasn't until they both retired from politics that they reconciled. Ironically they both died within hours of each other on the fiftieth anniversary of the signing of the Declaration of Independence, July 4th 1826.

So while they Founders were sometimes bitter rivals what did they believe? In the case of Jefferson it was quite radical. On the site Beliefnet you can find a version of Jefferson's Bible. A bible that he cut and pasted to assemble the teachings of Jesus without miracles and virgin birth. Jefferson said he wanted to separate the "diamonds from the dunghill." Exactly what did her remove from his version:
The virgin birth—gone.
Christ's bodily resurrection—gone.
The miracles of the loaves, walking on water, raising Lazarus—none of them made Jefferson's book

What about James Madison? Here are a few quotes:

"Ecclesiastical establishments tend to great ignorance and corruption, all of which facilitate the execution of mischievous projects."

and this

"What influence, in fact, have ecclesiastical establishments had on society? In some instances they have been seen to erect a spiritual tyranny on the ruins of the civil authority; on many instances they have been seen upholding the thrones of political tyranny; in no instance have they been the guardians of the liberties of the people."

Jefferson and Madison are just two examples. Adams was a Unitarian and didn't believe in the concept of the Trinity or the Divinity of Jesus... To say these men were not christian would be a stretch but to say the wanted to establish the United States as a christian nation would also be a stretch.